Driver circuit for an electric vehicle and a diagnostic method for determining when a first voltage driver is shorted to a low voltage and a second voltage driver is shorted to a high voltage

ABSTRACT

A driver circuit and a diagnostic method are provided. The driver circuit includes a first voltage driver, a second voltage driver, and a microprocessor. The microprocessor generates a first pulse width modulated signal to induce the first voltage driver to output a second pulse width modulated signal to energize a contactor coil. The microprocessor sets a first diagnostic flag equal to a first value if a first filtered voltage value is less than a first threshold value. The microprocessor sets a second diagnostic flag equal to a second value if a second filtered voltage value is greater than a second threshold value. The microprocessor stops generating the first pulse width modulated signal to de-energize the contactor coil if the first and second diagnostic flags are set equal to the first and second values, respectively.

BACKGROUND

The inventor herein has recognized a need for an improved driver circuitfor an electric vehicle and a diagnostic method for determining when afirst voltage driver is shorted to a low voltage and a second voltagedriver is shorted to a high voltage.

SUMMARY

A driver circuit for an electric vehicle in accordance with an exemplaryembodiment is provided. The driver circuit includes a first voltagedriver having a first input line, a first output line, and a firstvoltage sense line. The first input line is coupled to both the firstvoltage driver and a microprocessor. The first output line is coupled toa first side of a contactor coil of a contactor. The first voltage senseline is coupled to both the first output line and to the microprocessor.The driver circuit further includes a second voltage driver having asecond input line, a second output line, and a second voltage senseline. The second input line is coupled to the microprocessor. The secondoutput line is coupled to a second side of the contactor coil. Thesecond voltage sense line is coupled to the microprocessor. Themicroprocessor is configured to generate a first pulse width modulatedsignal on the first input line to induce the first voltage driver tooutput a second pulse width modulated signal on the first output linethat is received by the first side of the contactor coil to energize thecontactor coil. The microprocessor is further configured to iterativelymeasure a voltage on the first voltage sense line over time to obtain afirst plurality of voltage values when the microprocessor is generatingthe first pulse width modulated signal. The microprocessor is furtherconfigured to determine a first filtered voltage value based on thefirst plurality of voltage values. The microprocessor is furtherconfigured to set a first diagnostic flag equal to a first value if thefirst filtered voltage value is less than a first threshold value. Themicroprocessor is further configured to iteratively measure a voltage onthe second voltage sense line over time that is indicative of a voltageon the second output line to obtain a second plurality of voltage valueswhen the microprocessor is generating the first pulse width modulatedsignal. The microprocessor is further configured to determine a secondfiltered voltage value based on the second plurality of voltage values.The microprocessor is further configured to set a second diagnostic flagequal to a second value if the second filtered voltage value is greaterthan a second threshold value. The microprocessor is further configuredto stop generating the first pulse width modulated signal to de-energizethe contactor coil if the first diagnostic flag is set equal to thefirst value, and the second diagnostic flag is set equal to the secondvalue.

A diagnostic method for a driver circuit for an electric vehicle inaccordance with another exemplary embodiment is provided. The drivercircuit has a first voltage driver, a second voltage driver, and amicroprocessor. The first voltage driver has a first input line, a firstoutput line, and a first voltage sense line. The first input line iscoupled to both the first voltage driver and the microprocessor. Thefirst output line is coupled to a first side of a contactor coil of acontactor. The first voltage sense line is coupled to both the firstoutput line and to the microprocessor. The second voltage driver has asecond input line, a second output line, and a second voltage senseline. The second input line is coupled to the microprocessor. The secondoutput line is coupled to a second side of the contactor coil. Thesecond voltage sense line is coupled to the microprocessor. The methodincludes generating a first pulse width modulated signal on the firstinput line utilizing the microprocessor to induce the first voltagedriver to output a second pulse width modulated signal on the firstoutput line that is received by the first side of the contactor coil toenergize the contactor coil. The method further includes iterativelymeasuring a voltage on the first voltage sense line over time utilizingthe microprocessor to obtain a first plurality of voltage values whenthe microprocessor is generating the first pulse width modulated signal.The method further includes determining a first filtered voltage valuebased on the first plurality of voltage values utilizing themicroprocessor. The method further includes setting a first diagnosticflag equal to a first value if the first filtered voltage value is lessthan a first threshold value utilizing the microprocessor. The methodfurther includes iteratively measuring a voltage on the second voltagesense line over time that is indicative of a voltage on the secondoutput line utilizing the microprocessor to obtain a second plurality ofvoltage values when the microprocessor is generating the first pulsewidth modulated signal. The method further includes determining a secondfiltered voltage value based on the second plurality of voltage valuesutilizing the microprocessor. The method further includes setting asecond diagnostic flag equal to a second value if the second filteredvoltage value is greater than a second threshold value utilizing themicroprocessor. The method further includes stopping the generating ofthe first pulse width modulated signal to de-energize the contactor coilif the first diagnostic flag is set equal to the first value and thesecond diagnostic flag is set equal to the second value, utilizing themicroprocessor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an electric vehicle having a driver circuitin accordance with an exemplary embodiment;

FIG. 2 is a schematic of a first voltage driver utilized in the drivercircuit of FIG. 1;

FIG. 3 is a schematic of a second voltage driver utilized in the drivercircuit of FIG. 1;

FIG. 4 is a schematic of a first set of voltage pulses output by thedriver circuit of FIG. 1;

FIG. 5 is a schematic of a second set of voltage pulses output by thedriver circuit of FIG. 1;

FIG. 6 is a schematic of a signal output by the driver circuit of FIG.1;

FIG. 7 is a schematic of a third set of voltage pulses output by thedriver circuit of FIG. 1;

FIG. 8 is a schematic of a fourth set of voltage pulses output by thedriver circuit of FIG. 1;

FIG. 9 is a schematic of another signal output by the driver circuit ofFIG. 1;

FIG. 10 is a schematic of a fifth set of voltage pulses output by thedriver circuit of FIG. 1;

FIG. 11 is a schematic of a sixth set of voltage pulses output by thedriver circuit of FIG. 1;

FIG. 12 is a schematic of another signal output by the driver circuit ofFIG. 1; and

FIGS. 13-16 are flowcharts of a diagnostic method in accordance withanother exemplary embodiment.

DETAILED DESCRIPTION

Referring to FIGS. 1-3, an electric vehicle 10 having a driver circuit40 in accordance with an exemplary embodiment is provided. The electricvehicle 10 further includes a battery pack 30, a main contactor 50, agrounding contactor 52, a pre-charge contactor 54, a current sensor 60,a resistor 70, a high voltage inverter 90, an electrical motor 91,electrical lines 100, 102, 104, 106, 108, 114, 116, 118, and a vehiclecontroller 117. An advantage of the driver circuit 40 is that the drivercircuit 40 performs a diagnostic algorithm to determine when the drivercircuit 40 has a first voltage driver that is shorted to a low voltageand a second voltage driver that is shorted to a high voltage, as willbe explained in greater detail below.

Before explaining the structure and operation of the electric vehicle10, a brief explanation of some of the terms utilized herein will beprovided.

The term “filtered voltage value” refers to a voltage value that isdetermined based on a plurality of voltage values. A filtered voltagevalue can be determined utilizing a filter equation.

The term “filtered current value” refers to a current value that isdetermined based on a plurality of voltage values or a plurality ofcurrent values. A filtered current value can be determined utilizing afilter equation.

The term “filter equation” refers to an equation that is used tocalculate a value based on a plurality of values. In exemplaryembodiments, a filter equation can comprise a first order lag filter oran integrator for example. Of course, other types of filter equationsknown to those skilled in the art could be utilized.

The term “high voltage” refers to a voltage greater than an expectedvoltage during a predetermined operational mode of the driver circuit.For example, if an expected voltage at a predetermined location in thedriver circuit is 4 volts (e.g., 12 volts at a 30% duty cycle) in apredetermined operational mode of the driver circuit, an actual voltageof 4.5 volts at the predetermined location in the driver circuit couldbe considered a high voltage.

The term “high logic voltage” refers to a voltage in the driver circuitthat corresponds to a Boolean logic value of “1.”

The battery pack 30 is configured to output an operational voltage tothe high voltage inverter 90 which outputs operational voltages to theelectric motor 91 via the electrical lines 118. The battery pack 30includes battery modules 140, 142, 144 electrically coupled in serieswith one another.

The driver circuit 40 is configured to control operational positions ofthe main contactor 50, the grounding contactor 52, and the pre-chargecontactor 54. The driver circuit 40 includes a microprocessor 170, afirst voltage driver 180, a second voltage driver 182, a third voltagedriver 184, a fourth voltage driver 186, a fifth voltage driver 188, anda sixth voltage driver 190.

The microprocessor 170 is configured to generate control signals forcontrolling operation of the first voltage driver 180, the secondvoltage driver 182, the third voltage driver 184, the fourth voltagedriver 186, the fifth voltage driver 188, and the sixth voltage driver190. The microprocessor 170 is further configured to execute a softwareprogram stored in a memory device 171 for implementing a diagnosticalgorithm associated with the driver circuit 40 as will be explainedbelow. The memory device 171 is configured to store software algorithms,values, and status flags therein. The microprocessor 170 is operablycoupled to a Vcc voltage source that supplies an operational voltage(e.g., 5 Volts) to the microprocessor 170.

Before explaining the diagnostic algorithm associated with the drivercircuit 40 in accordance with an exemplary embodiment, the structure andoperation of the driver circuit 40 will be explained.

Referring to FIGS. 1 and 2, the first voltage driver 180 and the secondvoltage driver 182 are utilized to energize the main contactor coil 502to induce the contact 500 to have a closed operational position, and tode-energize the main contactor coil 502 to induce the contact 500 tohave an open operational position.

Referring to FIGS. 1 and 4-6, during operation, when the microprocessor170 outputs both the initial voltage pulse 602, and the first signal 702on the input lines 202, 262, respectively, of the first and secondvoltage drivers 180, 182, respectively; the voltage drivers 180, 182energize the main contactor coil 502 to induce the contact 500 to have aclosed operational position. In particular, in response to the firstvoltage driver 180 receiving the initial voltage pulse 602, the firstvoltage driver 180 outputs the initial voltage pulse 652 to energize themain contactor coil 502.

After generating the initial voltage pulse 602, the microprocessor 170outputs the pulse width modulated signal 603 having the voltage pulses604, 606, 608, 610 with a duty cycle of about 30%. Of course, the dutycycle of the voltage pulses 604, 606, 608, 610 could be less than 30% orgreater than 30%.

Further, after generating the initial voltage pulse 602, themicroprocessor 170 continues outputting the first signal 702 which has ahigh logic voltage while generating the voltage pulses 604, 606, 608,610. The first signal 702 turns on the transistor 280 in the secondvoltage driver 182.

In particular, in response to the first voltage driver 180 receiving thepulse width modulated signal 603, the first voltage driver 180 outputsthe pulse width modulated signal 653 (shown in FIG. 5) to maintainenergization the main contactor coil 502. The pulse width modulatedsignal 653 includes the voltage pulses 654, 656, 658, 660 with a dutycycle of about 30%. Of course, the duty cycle of the voltage pulses 654,656, 658, 660 could be less than 30% or greater than 30%.

When the microprocessor 170 stops outputting the pulse width modulatedsignal 603 and the first signal 702 on the input lines 202, 262,respectively, of the first and second voltage drivers 180, 182,respectively, the voltage drivers 180, 182 de-energize the maincontactor coil 502 to induce the contact 500 to have an open operationalposition.

Referring to FIGS. 1 and 2, the first voltage driver 180 includes adriver circuit 201, an input line 202, an output line 204, and a voltagesense line 206. The input line 202 is coupled to both the microprocessor170 and to the driver circuit 201. The output line 204 is electricallycoupled to a first side of the main contactor coil 502. The voltagesense line 206 is coupled to both the output line 204 and to themicroprocessor 170.

In one exemplary embodiment, the driver circuit 201 includes transistors220, 222. The transistor 220 has: (i) a base (B) coupled to a node 230that is further coupled to the microprocessor 170, (ii) a collector (C)coupled to a PSR voltage source, and (iii) an emitter coupled to a node232 which is further coupled to the output line 204. The transistor 222has: (i) a base (B) coupled to the node 230 that is further coupled tothe microprocessor 170, (ii) a collector (C) coupled to electricalground, and (iii) an emitter coupled to the node 232. When themicroprocessor 170 applies a high logic voltage to node 230, thetransistor 220 is turned on and the transistor 222 is turned off and avoltage (e.g., 12 volts) from the PSR voltage source is applied to thenode 232 and the output line 204 which is further applied to a first endof the main contactor coil 502. Alternately, when the microprocessor 170stops applying the high logic voltage to node 230, the transistor 220 isturned off and the transistor 222 is turned on and a ground voltage isapplied to the node 232 and the output line 204 which is further appliedto the first end of the main contactor coil 502.

Referring to FIGS. 1 and 3, the second voltage driver 182 includes adriver circuit 261, an input line 262, an output line 264, a voltagesense line 266, and a voltage sense line 268. The input line 262 iscoupled to both the microprocessor 170 and to the driver circuit 261.The output line 264 is electrically coupled to a second side of the maincontactor coil 502. The voltage sense line 266 coupled to both theoutput line 264 and to the microprocessor 170. When the main contactorcoil 502 is energized, the voltage sense line 268 receives a voltageindicative of a first current in the main contactor coil 502 and iscoupled to the microprocessor 170.

In one exemplary embodiment, the driver circuit 261 includes atransistor 280 and a resistor 282. The transistor 280 has: (i) a gate(G) coupled to the microprocessor 170, (ii) a drain (D) coupled to anode 284 that is further coupled to both the voltage sense line 266 andto the output line 264, and (iii) a source (S) coupled to a resistor282. The resistor 282 is coupled between the source (S) and electricalground. A node 286 at a first end of the resistor 282 is further coupledto the microprocessor 170 through the voltage sense line 268. When themicroprocessor 170 applies a high logic voltage to the gate (G), thetransistor 280 turns on and allows electrical current from the maincontactor coil 502 to flow through the transistor 280 and the resistor282 to ground. Alternately, when the microprocessor 170 stops applyingthe high logic voltage to the gate (G), the transistor 280 turns off anddoes not allow electrical current to flow through the main contactorcoil 502, the transistor 280, and the resistor 282.

Referring to FIG. 1, the third voltage driver 184 and the fourth voltagedriver 186 are utilized to energize the grounding contactor coil 512 toinduce the contact 510 to have a closed operational position, and tode-energize the grounding contactor coil 512 to induce the contact 510to have an open operational position.

Referring to FIGS. 1 and 7-9, during operation, when the microprocessor170 outputs both the initial voltage pulse 802, and the first signal 902on the input lines 302, 362 of the third and fourth voltage drivers 184,186, respectively; the voltage drivers 184, 186 energize the groundingcontactor coil 512 to induce the contact 510 to have a closedoperational position. In particular, in response to the third voltagedriver 184 receiving the initial voltage pulse 802, the third voltagedriver 184 outputs the initial voltage pulse 852 to energize thegrounding contactor coil 512.

After generating the initial voltage pulse 802, the microprocessor 170outputs the pulse width modulated signal 803 having the voltage pulses804, 806, 808, 810 with a duty cycle of about 30%. Of course, the dutycycle of the voltage pulses 804, 806, 808, 810 could be less than 30% orgreater than 30%.

Further, after generating the initial voltage pulse 802, themicroprocessor 170 continues outputting the first signal 902 which has ahigh logic voltage while generating the voltage pulses 804, 806, 808,810, to continue to turn on a transistor, like the transistor 280, inthe fourth voltage driver 186.

In particular, in response to the third voltage driver 184 receiving thepulse width modulated signal 803, the third voltage driver 184 outputsthe pulse width modulated signal 853 (shown in FIG. 8) to energize thegrounding contactor coil 512. The pulse width modulated signal 853includes the voltage pulses 854, 856, 858, 860 having a duty cycle ofabout 30%. Of course, the duty cycle of the voltage pulses 854, 856,858, 860 could be less than 30% or greater than 30%.

When the microprocessor 170 stops outputting the pulse width modulatedsignal 803, and the first signal 902 on the input lines 302, 362,respectively, of the third and fourth voltage drivers 184, 186,respectively, the voltage drivers 184, 186 de-energize the groundingcontactor coil 512 to induce the contact 510 to have an open operationalposition.

Referring to FIGS. 1 and 2, the third voltage driver 184 includes adriver circuit 301, an input line 302, an output line 304, and a voltagesense line 306. The input line 302 is coupled to both the microprocessor170 and to the driver circuit 301. The output line 304 is electricallycoupled to a first side of the grounding contactor coil 512. The voltagesense line 306 is coupled to both the output line 304 and to themicroprocessor 170. In one exemplary embodiment, the structure of thedriver circuit 301 is identical to the structure of the driver circuit201 discussed above.

Referring to FIGS. 1 and 3, the fourth voltage driver 186 includes adriver circuit 361, an input line 362, an output line 364, a voltagesense line 366, and a voltage sense line 368. The input line 362 iscoupled to both the microprocessor 170 and to the driver circuit 361.The output line 364 is electrically coupled to a second side of thegrounding contactor coil 512. The voltage sense line 366 coupled to boththe output line 364 and to the microprocessor 170. When the groundingcontactor coil 512 is energized, the voltage sense line 368 receives asignal indicative of a second current in the grounding contactor coil512 and is coupled to the microprocessor 170. In one exemplaryembodiment, the structure of the driver circuit 361 is identical to thestructure of the driver circuit 261.

The fifth voltage driver 188 and the sixth voltage driver 190 areutilized to energize the pre-charge contactor coil 522 to induce thecontact 520 to have a closed operational position, and to de-energizethe pre-charge contactor coil 522 to induce the contact 520 to have anopen operational position.

Referring to FIGS. 1 and 10-12, during operation, when themicroprocessor 170 outputs both the initial voltage pulse 1002, and thefirst signal 1102 on the input lines 402, 462, respectively, of thefifth and sixth voltage drivers 188, 190, respectively; the voltagedrivers 188, 190 energize the pre-charge contactor coil 522 to inducethe contact 520 to have a closed operational position. In particular, inresponse to the fifth voltage driver 188 receiving the initial voltagepulse 1002, the fifth voltage driver 188 outputs the initial voltagepulse 1052 to energize the grounding contactor coil 512.

After generating the initial voltage pulse 1002, the microprocessor 170outputs the pulse width modulated signal 1003 having the voltage pulses1004, 1006, 1008, 1010 with a duty cycle of about 30%. Of course, theduty cycle of the voltage pulses 1004, 1006, 1008, 1010 could be lessthan 30% or greater than 30%.

Further, after generating the initial voltage pulse 1002, themicroprocessor 170 continues outputting the first signal 1102 which hasa high logic voltage while generating the voltage pulses 1004, 1006,1008, 1010, to continue to turn on a transistor, like the transistor280, in the sixth voltage driver 190.

In response to the fifth voltage driver 188 receiving the pulse widthmodulated signal 1003, the fifth voltage driver 188 outputs the pulsewidth modulated signal 1053 to energize the pre-charge contactor coil522. The pulse width modulated signal 1053 includes the voltage pulses1054, 1056, 1058, 1060 having a duty cycle of about 30%. Of course, theduty cycle of the voltage pulses 1054, 1056, 1058, 1060 could be lessthan 30% or greater than 30%.

When the microprocessor 170 stops outputting the pulse width modulatedsignal 1003, and the first signal 1102 on the input lines 402, 462,respectively, of the fifth and sixth voltage drivers 188, 190,respectively; the voltage drivers 188, 190 de-energize the pre-chargecontactor coil 522 to induce the contact 520 to have an open operationalposition.

The fifth voltage driver 188 includes a driver circuit 401, an inputline 402, an output line 404, and a voltage sense line 406. The inputline 402 is coupled to both the microprocessor 170 and to the drivercircuit 401. The output line 404 is electrically coupled to a first sideof the pre-charge contactor coil 522. The voltage sense line 406 iscoupled to both the output line 404 and to the microprocessor 170. Inone exemplary embodiment, the structure of the driver circuit 401 isidentical to the structure of the driver circuit 201 discussed above.

The sixth voltage driver 190 includes a driver circuit 461, an inputline 462, an output line 464, a voltage sense line 466, a voltage senseline 468. The input line 462 is coupled to both the microprocessor 170and to the driver circuit 461. The output line 464 is electricallycoupled to a second side of the pre-charge contactor coil 522. Thevoltage sense line 466 coupled to both the output line 464 and to themicroprocessor 170. When the pre-charge contactor coil 522 is energized,the voltage sense line 468 receives a signal indicative of a thirdcurrent in the pre-charge contactor coil 522 and is coupled to themicroprocessor 170. In one exemplary embodiment, the structure of thedriver circuit 461 is identical to the structure of the driver circuit261.

The main contactor 50 is electrically coupled in series with the batterypack 30, the current sensor 60 and the inverter 90. In particular, apositive voltage terminal of the battery pack 100 is electricallycoupled to the current sensor 60 via the electrical line 100. Thecurrent sensor 60 is electrically coupled to a first end of the contact500 of the main contactor 50 via the electrical line 102. Also, a secondend of the contact 500 is electrically coupled to the inverter 90 viathe electrical line 106. When the main contactor coil 502 is energized,the contact 500 has a closed operational position and electricallycouples a positive voltage terminal of the battery pack 30 to theinverter 90. When the main contactor coil 502 is de-energized, thecontact 500 has an open operational position and electrically de-couplesthe positive voltage terminal of the battery pack 30 from the inverter90.

The grounding contactor 52 is electrically coupled in series between thebattery pack 30 and the inverter 90. A negative voltage terminal of thebattery pack 30 is electrically coupled to a first end of the contact510 of the grounding contactor 52 via the electrical line 114. Also, asecond end of the contact 510 is electrically coupled to the inverter 90via the electrical line 116. When the grounding contactor coil 512 isenergized, the contact 510 has a closed operational position andelectrically couples a negative voltage terminal of the battery pack 30to the inverter 90. When the grounding contactor coil 512 isde-energized, the contact 510 has an open operational position andelectrically de-couples the negative voltage terminal of the batterypack 30 from the inverter 90.

The pre-charge contactor 54 is electrically coupled in parallel to themain contactor 50. A first end of the contact 520 is electricallycoupled to the electrical line 102 via the electrical line 104. A secondend of the contact 520 is electrically coupled to the electrical line106 via the resistor 70 and the electrical line 108. When the pre-chargecontactor coil 522 is energized, the contact 520 has a closedoperational position and electrically couples a positive voltageterminal of the battery pack 30 to the inverter 90. When the pre-chargecontactor coil 522 is de-energized, the contact 520 has an openoperational position and electrically de-couples the positive voltageterminal of the battery pack 30 from the inverter 90.

The current sensor 60 is configured to generate a signal indicative of atotal amount of current being supplied by the battery pack 30 to theinverter 90. The microprocessor 170 receives the signal from the currentsensor 60. The current sensor 60 is electrically coupled in seriesbetween a positive voltage terminal of the battery pack 30 and a firstend of the contact 500.

Referring to FIGS. 1, 4-6, and 13-16, a flowchart of diagnostic methodfor the driver circuit 40 of the electric vehicle 10 when at least oneof the main contactor coil 502, the grounding contactor coil 512, andthe pre-charge contactor coil 522 are energized will now be explained.For purposes of simplicity, the following diagnostic method will beexplained with reference to the main contactor coil 502 and the firstand second voltage drivers 180, 182 for controlling the main contactorcoil 502. However, it should be understood that the following diagnosticmethod can be utilized with grounding contactor coil 512 and/or thepre-charge contactor coil 522 and the associated voltage driverstherewith.

At step 1300, the driver circuit 40 has the first voltage driver 180,the second voltage driver 182 and the microprocessor 170. The firstvoltage driver 180 has the input line 202, the output line 204, and thevoltage sense line 206. The input line 202 is coupled to both the firstvoltage driver 180 and the microprocessor 170. The output line 204 iscoupled to a first side of the contactor coil 502 of the contactor 50.The voltage sense line 206 is coupled to both the output line 204 and tothe microprocessor 170. The second voltage driver 182 has the input line262, the output line 264, and the voltage sense line 268. The input line262 is coupled to the microprocessor 170. The output line 264 is coupledto a second side of the contactor coil 502. The voltage sense line 268is coupled to microprocessor 170, and is electrically coupled to theoutput line 264 via the transistor 280.

At step 1302, the microprocessor 170 sets each of the first, second,third, fourth, fifth, and sixth diagnostic flags to an initial value. Inone exemplary embodiment, the initial value is a Boolean logic value of“0.” After step 1302, the method advances to step 1304.

At step 1304, the microprocessor 170 generates a first pulse widthmodulated signal 603 on the input line 202 to induce the first voltagedriver 180 to output a second pulse width modulated signal 653 on theoutput line 204 that is received by the first side of the contactor coil502. After step 1304, the method advances to step 1306.

At step 1306, the microprocessor 170 generates a first signal 702 on theinput line 262, while generating the first pulse width modulated signal,to induce the second voltage driver 182 to receive an electrical currentfrom the contactor coil 502 on the output line 264 which energizes thecontactor coil 502. After step 1306, the method advances to step 1320.

At step 1320, the microprocessor 170 iteratively measures a voltage onthe voltage sense line 206 over time to obtain a first plurality ofvoltage values when the microprocessor 170 is generating the first pulsewidth modulated signal 603. After step 1320, the method advances to step1322.

At step 1322, the microprocessor 170 determines a first filtered voltagevalue based on the first plurality of voltage values utilizing a firstfilter equation. In one exemplary embodiment, the first filter equationis a first order lag filter equation. For example, in one exemplaryembodiment, the first filter equation is as follows: first filteredvoltage value=first filtered voltage value_(Old)+(voltage value of oneof first plurality of voltage values−first filtered voltagevalue_(Old))*Gain_(Calibration). It is noted that the foregoing equationis iteratively calculated utilizing each of the voltage values of thefirst plurality of voltage values. After step 1322, the method advancesto step 1324.

At step 1324, the microprocessor 170 iteratively measures a voltage onthe voltage sense line 268 over time to obtain a second plurality ofvoltage values when the microprocessor 170 is generating the first pulsewidth modulated signal 603. The voltage on the voltage sense line 268 isindicative of a voltage on the output line 264 (e.g., voltage on outputline 264=voltage on voltage sense line 268+voltage drop across thetransistor 280) when the transistor 280 is turned on. After step 1324,the method advances to step 1326.

At step 1326, the microprocessor 170 determines a second filteredvoltage value based on the second plurality of voltage values utilizinga second filter equation. In one exemplary embodiment, the second filterequation is a first order lag filter equation. For example, in oneexemplary embodiment, the second filter equation is as follows: secondfiltered voltage value=second filtered voltage value_(Old)+(voltagevalue of one of second plurality of voltage values−second filteredvoltage value_(Old))*Gain_(Calibration). It is noted that the foregoingequation is iteratively calculated utilizing each of the voltage valuesof the second plurality of voltage values. After step 1326, the methodadvances to step 1328.

At step 1328, the microprocessor 170 makes a determination as to whetherthe first filtered voltage value is less than a first threshold valueindicating that the first voltage driver 180 is undesirably shorted to alow voltage. If the value of step 1328 equals “yes”, the method advancesto step 1330. Otherwise, the method advances to step 1340.

At step 1330, the microprocessor 170 sets a first diagnostic flag equalto a first value. In one exemplary embodiment, the first value is aBoolean logic value of “1.” After step 1330, the method advances to step1332.

At step 1332, the microprocessor 170 makes a determination as to whetherthe second filtered voltage value is greater than a second thresholdvalue indicating that the second voltage driver 182 is undesirablyshorted to a high voltage. If the value of step 1322 equals “yes”, themethod advances to step 1334. Otherwise, the method advances to step1340.

At step 1334, the microprocessor 170 sets a second diagnostic flag equalto a second value. In one exemplary embodiment, the second value is aBoolean logic value of “1.” After step 1334, the method advances to step1340.

Referring again to step 1328, if the value of step 1328 equals “no”, themethod advances to step 1340. At step 1340, the microprocessor 170 makesa determination as to whether the first diagnostic flag is set equal tothe first value, and whether the second diagnostic flag is set equal tothe second value, indicating that the contactor coil 502 is beingenergized by a reversed polarity voltage. If the value of step 1340equals “yes”, the method advances to step 1342. Otherwise, the methodadvances to step 1344.

At step 1342, the microprocessor 170 stops generating the first pulsewidth modulated signal 603 and the first signal 702 to de-energize thecontactor coil 502. After step 1342, the method is exited.

Referring again to step 1340, if the value of step 1340 equals “no”, themethod advances to step 1344. At step 1344, the microprocessor 170 makesa determination as to whether the second filtered voltage value isgreater than a third threshold value indicating that the second voltagedriver 182 is undesirably shorted to a high voltage. If the value ofstep 1344 equals “yes’, the method advances to step 1346. Otherwise, themethod advances to step 1352.

At step 1346, the microprocessor 170 sets a third diagnostic flag equalto a third value. In one exemplary embodiment, the third value is aBoolean logic value of “1.” After step 1346, the method advances to step1348.

At step 1348, the microprocessor 170 makes a determination as to whetherthe first filtered voltage value is greater than a fourth thresholdvalue indicating that the first voltage driver 180 is undesirablyshorted to a high voltage. If the value of step 1348 equals “yes”, themethod advances to step 1350. Otherwise, the method advances to step1352.

At step 1350, the microprocessor 170 sets a fourth diagnostic flag equalto a fourth value. In one exemplary embodiment, the fourth value is aBoolean logic value of “1.” After step 1350, the method advances to step1352.

Referring again to step 1344, if the value of step 1344 equals “no”, themethod advances to step 1352. At step 1352, the microprocessor 170 makesa determination as to whether the fourth diagnostic flag is set equal tothe fourth value indicating that the first voltage driver 180 isundesirably shorted to a high voltage, and whether the third diagnosticflag is set equal to the third value indicating that the second voltagedriver 182 is undesirably shorted to a high voltage. If the value ofstep 1352 equals “yes’, the method advances to step 1370. Otherwise, themethod advances to step 1372.

At step 1370, the microprocessor 170 stops generating the first pulsewidth modulated signal 603 and the first signal 702 to de-energize thecontactor coil 502. After step 1370, the method is exited.

Referring again to step 1352, if the value of step 1352 equals “no”, themethod advances to step 1372. At step 1372, the microprocessor 170 makesa determination as to whether the first filtered voltage value isgreater than a fifth threshold value indicating that the first voltagedriver 180 is undesirably shorted to a high voltage. If the value ofstep 1372 equals “yes”, the method advances to step 1374. Otherwise, themethod advances to step 1382.

At step 1374, the microprocessor 170 sets a fifth diagnostic flag equalto a fifth value. In one exemplary embodiment, the fifth value is aBoolean logic value of “1.” After step 1374, the method advances to step1376.

At step 1376, the microprocessor 170 determines a first filtered currentvalue based on the second plurality of voltage values. In one exemplaryembodiment, the first filtered current equation is a first order lagfilter equation. For example, in one exemplary embodiment, the firstfiltered current equation is as follows: first filtered currentvalue=first filtered current value_(Old)+((voltage value of one ofsecond plurality of voltage values/resistance of resistor 282)−firstfiltered current value_(Old)))*Gain_(Calibration). It is noted that theforegoing equation is iteratively calculated utilizing each of thevoltage values of the second plurality of voltage values. The firstfiltered current value is indicative of an amount of electrical currentflowing through the contactor coil 502. After step 1376, the methodadvances to step 1378.

At step 1378, the microprocessor 170 makes a determination as to whetherthe first filtered current value is less than a sixth threshold value.If the value of step 1378 equals “yes”, the method advances to step1380. Otherwise, the method advances to step 1382.

At step 1380, the microprocessor 170 sets a sixth diagnostic flag equalto a sixth value. In one exemplary embodiment, the sixth value is aBoolean logic value of “1.” After step 1380, the method advances to step1382.

Referring again to step 1372, if the value of step 1372 equals “no”, themethod advances to step 1382. At step 1382, the microprocessor makes adetermination as to whether the fifth diagnostic flag is set equal tothe fifth value, and whether the sixth diagnostic flag is set equal tothe sixth value, indicating that the amount of electrical currentflowing through the contactor coil 502 is less than a desired electricalcurrent level that maintains a closed operational state of the contactor50. If the value of step 1382 equals “yes’, the method advances to step1384. Otherwise, the method is exited.

At step 1384, the microprocessor 170 stops generating the first pulsewidth modulated signal 603 and the first signal 702 to de-energize thecontactor coil 502. After step 1384, the method is exited.

The driver circuit 40 and the diagnostic method provide a substantialadvantage over other circuits and methods. In particular, the drivercircuit 40 and the diagnostic method provide a technical effect ofdetermining when a first voltage driver is shorted to a low voltage anda second voltage driver is shorted to a high voltage.

The above-described diagnostic method can be at least partially embodiedin the form of one or more computer readable media havingcomputer-executable instructions for practicing the methods. Thecomputer-readable media can comprise one or more of the following: harddrives, RAM memory, flash memory, and other computer-readable mediaknown to those skilled in the art; wherein, when the computer-executableinstructions are loaded into and executed by one or more computers ormicroprocessors, the one or more computers or microprocessors become anapparatus for practicing the methods.

While the claimed invention has been described in detail in connectionwith only a limited number of embodiments, it should be readilyunderstood that the invention is not limited to such disclosedembodiments. Rather, the claimed invention can be modified toincorporate any number of variations, alterations, substitutions orequivalent arrangements not heretofore described, but which arecommensurate with the spirit and scope of the invention. Additionally,while various embodiments of the claimed invention have been described,it is to be understood that aspects of the invention may include onlysome of the described embodiments. Accordingly, the claimed invention isnot to be seen as limited by the foregoing description.

What is claimed is:
 1. A driver circuit for an electric vehicle,comprising: a first voltage driver having a first input line, a firstoutput line, and a first voltage sense line; the first input linecoupled to both the first voltage driver and a microprocessor, the firstoutput line coupled to a first side of a contactor coil of a contactor,the first voltage sense line coupled to both the first output line andto the microprocessor; a second voltage driver having a second inputline, a second output line, and a second voltage sense line; the secondinput line coupled to the microprocessor, the second output line coupledto a second side of the contactor coil, the second voltage sense linecoupled to the microprocessor; the microprocessor configured to generatea first pulse width modulated signal on the first input line to inducethe first voltage driver to output a second pulse width modulated signalon the first output line that is received by the first side of thecontactor coil to energize the contactor coil; the microprocessorfurther configured to iteratively measure a voltage on the first voltagesense line over time to obtain a first plurality of voltage values whenthe microprocessor is generating the first pulse width modulated signal;the microprocessor further configured to determine a first filteredvoltage value based on the first plurality of voltage values; themicroprocessor further configured to set a first diagnostic flag equalto a first value if the first filtered voltage value is less than afirst threshold value; the microprocessor further configured toiteratively measure a voltage on the second voltage sense line over timethat is indicative of a voltage on the second output line to obtain asecond plurality of voltage values when the microprocessor is generatingthe first pulse width modulated signal; the microprocessor furtherconfigured to determine a second filtered voltage value based on thesecond plurality of voltage values; the microprocessor furtherconfigured to set a second diagnostic flag equal to a second value ifthe second filtered voltage value is greater than a second thresholdvalue; and the microprocessor further configured to stop generating thefirst pulse width modulated signal to de-energize the contactor coil ifthe first diagnostic flag is set equal to the first value, and thesecond diagnostic flag is set equal to the second value.
 2. The drivercircuit of claim 1, wherein the microprocessor is further configured togenerate a first signal on the second input line to induce the secondvoltage driver to receive an electrical current from the contactor coilon the second output line to energize the contactor coil.
 3. The drivercircuit of claim 2, wherein the microprocessor is further configured tostop generating the first signal to de-energize the contactor coil ifthe first diagnostic flag is set equal to the first value, and thesecond diagnostic flag is set equal to the second value.
 4. The drivercircuit of claim 2, wherein the first signal has a high logic voltagewhile the first pulse width modulated signal is being generated.
 5. Thedriver circuit of claim 1, wherein when the first diagnostic flag is setequal to the first value and the second diagnostic flag is set equal tothe first value, the first diagnostic flag indicates that the firstvoltage driver is shorted to a low voltage, and the second diagnosticflag indicates that the second voltage driver is shorted to a highvoltage, such that the contactor coil is being energized by a reversedpolarity voltage.
 6. The driver circuit of claim 1, wherein the secondthreshold value is greater than the first threshold value.
 7. The drivercircuit of claim 1, wherein the second voltage sense line iselectrically coupled to the second output line utilizing a transistor.8. A diagnostic method for a driver circuit for an electric vehicle, thedriver circuit having a first voltage driver, a second voltage driver,and a microprocessor; The first voltage driver having a first inputline, a first output line, and a first voltage sense line; the firstinput line coupled to both the first voltage driver and themicroprocessor, the first output line coupled to a first side of acontactor coil of a contactor, the first voltage sense line coupled toboth the first output line and to the microprocessor; the second voltagedriver having a second input line, a second output line, and a secondvoltage sense line; the second input line coupled to the microprocessor,the second output line coupled to a second side of the contactor coil,the second voltage sense line coupled to the microprocessor; the methodcomprising: generating a first pulse width modulated signal on the firstinput line utilizing the microprocessor to induce the first voltagedriver to output a second pulse width modulated signal on the firstoutput line that is received by the first side of the contactor coil toenergize the contactor coil; iteratively measuring a voltage on thefirst voltage sense line over time utilizing the microprocessor toobtain a first plurality of voltage values when the microprocessor isgenerating the first pulse width modulated signal; determining a firstfiltered voltage value based on the first plurality of voltage valuesutilizing the microprocessor; setting a first diagnostic flag equal to afirst value if the first filtered voltage value is less than a firstthreshold value utilizing the microprocessor; iteratively measuring avoltage on the second voltage sense line over time that is indicative ofa voltage on the second output line utilizing the microprocessor toobtain a second plurality of voltage values when the microprocessor isgenerating the first pulse width modulated signal; determining a secondfiltered voltage value based on the second plurality of voltage valuesutilizing the microprocessor; setting a second diagnostic flag equal toa second value if the second filtered voltage value is greater than asecond threshold value utilizing the microprocessor; and stopping thegenerating of the first pulse width modulated signal to de-energize thecontactor coil if the first diagnostic flag is set equal to the firstvalue and the second diagnostic flag is set equal to the second value,utilizing the microprocessor.
 9. The diagnostic method of claim 8,further comprising generating a first signal on the second input lineutilizing the microprocessor to induce the second voltage driver toreceive an electrical current from the contactor coil on the secondoutput line to energize the contactor coil.
 10. The diagnostic method ofclaim 9, further comprising stopping the generating of the first signalutilizing the microprocessor to de-energize the contactor coil if thefirst diagnostic flag is set equal to the first value, and the seconddiagnostic flag is set equal to the second value.
 11. The diagnosticmethod of claim 9, wherein the first signal has a high logic voltagewhile the first pulse width modulated signal is being generated.
 12. Thediagnostic method of claim 9, wherein when the first diagnostic flag isset equal to the first value and the second diagnostic flag is set equalto the first value, the first diagnostic flag indicates that the firstvoltage driver is shorted to a low voltage, and the second diagnosticflag indicates that the second voltage driver is shorted to a highvoltage, such that the contactor coil is being energized by a reversedpolarity voltage.
 13. The diagnostic method of claim 8, wherein thesecond threshold value is greater than the first threshold value. 14.The diagnostic method of claim 8, further comprising turning on atransistor to electrically couple the second voltage sense line to thesecond output line.